This invention relates to a piston for use in a cylinder having a piston rod fixed in axial relation thereto having annular wear surfaces on each side of a groove carrying a sealing ring.
Prior art piston assemblies such as those illustrated in U.S. Pat. No. 4,167,134 issued to Yuda, typically require only a wear ring to adequately reduce friction because of slower operating speeds and less demanding loads. However, the application of wear rings to a compact piston is an arduous process contributing significantly to the overall cost of the piston. Therefore, a less costly technique for reducing friction in a compact hydraulically operated piston is desirable.
According to the prior art, pistons have been supplied with Teflon wear rings and a rubber O-ring and the like in spaced relation thereto. Problems have been encountered in the manufacture due to the necessity of softening the Teflon ring before application thereof to the cylinder requiring boiling in oil to accomplish placement of the wear ring. Due to the necessity of utilizing an additional O-ring for purposes of sealing, the outer surfaces of the cylinder are of limited area. Furthermore, the extent of the wear surface provided by the Teflon ring is limited. As a result of side load friction upon the piston, galling and other damage to the bore of the cylinder results from contact by the piston therewith. An attempt to solve this problem is disclosed in U.S. Pat. No. 4,067,093 which contemplates disposing spaced molded wear members with a machined groove therebetween for placement of a sealing assembly therebetween. Many complicated manufacturing operations including molding and machining add to the expense, and the molded material is of limited effectiveness as a wear surface. Other U.S. patents dealing with the coating of a piston include U.S. Pat. Nos. 2,817,562, 3,890,950 and 4,724,819.
Accordingly, it is an important object of this invention to provide a piston for use in a cylinder assembly and having a piston rod fixed in axial relation thereto, which is of greatly reduced cost and which possesses superior wear characteristics.
Another important object of the invention is to provide a simplified method of manufacture for a piston having a piston rod fixed in axial relation thereto wherein improved wear characteristics are imparted thereto with improved performance of a cylinder assembly with which it is used.
Another object of the invention is to eliminate the usual wear ring with its difficulty of application, and to provide increased wear surface area.